Vented gravel packing system and method of use

ABSTRACT

An apparatus and method are disclosed for gravel packing an interval of a wellbore. The apparatus comprises a sand control screen generally comprising three main sections; a filter section, a blank pipe section, and a vent section. In one embodiment, the vent section comprises a removable vent. In another embodiment, the vent section comprises a vented valve assembly may remain downhole after gravel packing is complete. Both embodiments include a sand height control check valve for ensuring that the proper sand height of the gravel pack is achieved.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

FIELD OF THE INVENTION

The present invention relates to an improved vented gravel packing system for gravel packing production wells.

BACKGROUND OF THE INVENTION

In the petroleum industry, completion of a well drilled through subterranean formations generally involves lining the well with a casing and using a perforation gun to create perforation tunnels through the casing and the formation adjacent to the casing. The perforation tunnels are usually created adjacent to the formation production zones, which allow reservoir fluids to flow from the formation into the casing and to the surface. If the formation contains unconsolidated sand, the unconsolidated sand may flow from the formation into the well during production of the reservoir fluids. Typically, this production of sand is not desirable since the sand may choke surface equipment, erode the production string and the wellhead, and bridge the well such that further production from the well is prevented.

Production of sand along with reservoir fluids is not a new problem. Conventional means for control the production of sand include the technique know as gravel pack completion. Gravel pack completion involves placing a screen in the well adjacent to the perforation tunnels and filling an annular area between the screen and the casing, as well as the perforation tunnels, with coarse sand. The sand is delivered to the perforation tunnels as a fluid slurry by a liquid carrier. The slurry is pumped down to the perforation tunnels through the workstring and into the annular area between the screen and casing. Once complete, the resulting gravel pack is a highly porous, permeable layer of coarse sand, which filters formation sand form the reservoir fluids entering the well.

One commonly used techniques for the placement of sand in a gravel pack completion is the “squeeze technique.” Gravel is squeezed through the perforations to pack outside the casing and in the screen annulus without circulation. A squeeze packer with a crossover tool is used to place the gravel pack. The screen and the blank pipe are run in the hole and positioned across the productive interval. The packer is set and the crossover opened. The slurry is then “bullheaded” down a workstring, through the crossover tool, into the screen-casing annulus, and through the perforations in the casing. Pumping is continued until a pre-determined pressure increase or “sandout” pressure occurs, indicating that no more gravel can be “squeezed” outside of the casing or into the annulus. Once a “sandout” is achieved, pumping is discontinued and treatment pressures are vented before physically pulling the crossover tool to the “upper” circulating position. After the upper circulating position has been accomplished, pumping is resumed to circulate any excess gravel remaining in the workstring to the surface.

Another commonly used technique is referred to as the “one trip circulating technique.” A washpipe is positioned inside and extending through the screen to accommodate the circulation of fluids and gravel to the bottom of the screen. A gravel slurry is circulated down the tubing, through a crossover tool, down the screen-casing annulus, through the screen, up the washpipe, through the crossover tool and returns up the workstring-casing annulus. Gravel contained in the slurry is separated out of the circulating fluid as it passes through the screen.

As the screen is covered with gravel, the circulation pressure increases, forcing gravel into the perforations. Pumping is continued until a pre-determined pressure increase or “sandout” occurs indicating that no more gravel can be circulated outside of the casing or into the annulus. Once a “sandout” is achieved, pumping is discontinued and treatment pressures are vented before pulling the crossover tool to the “upper” circulating position. After the upper circulating position is accomplished, pumping is resumed to circulate out any excess gravel remaining in the workstring.

It has been found, however, that it is difficult to completely gravel pack production intervals. This is particularly true for deviated production intervals.

Conventional gravel pack systems generally include a pipe, referred to as a vent screen, consisting of three main sections. A lower most filtering section, a blank pipe section above the filtering section and a vent section above the blank pipe section. The filtering section of the pipe is located across the production zone of the formation and is the portion of the vent screen through which reservoir fluids will flow. The blank pipe section creates an annular region, along with the casing, in which the gravel pack is set to a predetermined height above the production zone of the formation. This predetermined height, or sand height, ensures the gravel pack remains in place and prevents reservoir fluids from bypassing the vent screen and flowing through the annular region between the vent screen and casing, an occurrence referred to as a failed gravel pack. The vent section maintains equilibrium inside the vent screen and in the annular region and prevents the collapse of the vent screen during gravel packing operations.

During gravel packing operations, pressure differential between the annular region created by the blank pipe section and the casing and the central portion of the vent screen may cause the liquid carrier to flow through the vent section and into the central area of the vent screen. When this occurs, sand may bridge across the outer surface of the vent section to the casing thereby preventing the proper sand height of the gravel pack from ever being achieved. The vent section can also become choked with sand, thereby hindering production of reservoir fluids.

In addition to the bridging of sand at the vent section, another problem associated with conventional gravel packing is the fact that the vent section of the vent screen adds additional pressure drop to the well, which reduces the flow of reservoir fluids from the formation. Also, if the vent section becomes choked, the pressure differential could potentially cause failure of the gravel pack.

SUMMARY OF THE INVENTION

The present invention addresses the problems associated with conventional gravel packing systems, by providing an improved vent screen and gravel pack operation. One preferred embodiment of the present invention generally comprises a vent screen with a removable vent section. After the gravel pack is completed, the vent section of the vent screen, which is attached to the vent screen by means of shear pins, is detached and recovered through the production string. After removal of the vent section, reservoir fluids are passed across the complete diameter of the vent screen, which eliminates the potential for choking and the resulting failure of the gravel pack. In another preferred embodiment of the present invention, a vented valve system is employed. The vented valve system generally comprises a check valve installed above the vent section of the vent screen. The check valve acts as a plug in the top of the vent screen during gravel pack operations, however, once reservoir fluids are allowed to flow through the vent screen, the reservoir fluids lift the check valve and flow upward to the production tubing. The vented valve system may also be attached via shear pins to allow the vented valve to be removed if the need arises. Mechanical packers may be used in both embodiments to prohibit reservoir fluids from flowing through the gravel pack as the pressure drop across the filter section of the vent screen builds.

In addition to the improved vent section, the present invention also includes a means for ensuring that the proper sand height is achieved at sandout. A check valve, referred to as a sand-height valve, is installed above the filter section and within the vent screen. The sand-height valve prevents the gravel pack carrier fluid from entering the filter section and flowing through to the perforation tunnels. The sand-height valve is attached to the vent screen with shear pins. The shear pins are designed to fail once sandout pressure is achieved, thus ensuring that the proper sand height has been attained in the annulus between the vent screen and the casing. Once the shear pins fail the sand-height valve drops to the bottom of the vent screen where it remains.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a production well illustrating a conventional vent screen and sand bridging across the vent section.

FIG. 2 is a cross-sectional view of production well illustrating one preferred embodiment of the present invention, featuring a removable vent and sand-height valve shown during gravel packing operations.

FIG. 3 is a cross-sectional view of production well illustrating one preferred embodiment of the present invention, featuring a removable vent and sand-height valve shown after completion of gravel packing operations and back on production.

FIG. 4 is a cross-sectional view of a production well illustrating another preferred embodiment of the present invention, featuring a vented valve vent section and sand height valve shown during gravel packing operations.

FIG. 5 is a cross-sectional view of a production well illustrating another preferred embodiment of the present invention, featuring a vented valve vent section and sand height valve shown after completion of gravel packing operations and back on production.

PREFERRED EMBODIMENTS OF THE INVENTION

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

FIG. 1 illustrates, a conventional vent screen application. Tubing 10 within casing 20 delivers the gravel pack slurry 25 to the production interval 30. The vent screen 50 generally comprises three main sections: the filter section 52; the blank pipe section 54; and the vent section 56. Gravel pack slurry 25 is diverted into the annular region 60 between vent screen 50 and casing 20 by vent screen plug 58. However, as the gravel pack 70 builds and the pressure in annular region 60 rises, the fluid carrier of gravel pack slurry 25 is forced into vent section 56 and travels down the internal area 65 of vent screen 50. Vent section 56 filters out the sand in gravel pack slurry 25 and the sand can form a bridge 70 in the annular space 62 between the vent section 56 of vent screen 50 and the casing 20. The bridge 70 of sand prohibits the completion of gravel pack.

FIGS. 2 and 3 illustrate one preferred embodiment of a vent screen application of the present invention. The figures show a schematic representation of a production well. The wellbore extends through the various earth strata including formation 110. A casing is cemented within wellbore by cement. The workstring 103 includes gravel packing apparatus 100 for gravel packing an interval of the wellbore adjacent to formation 110 and between mechanical packers 101, 102. The workstring 103 may also include other various tools.

Even though the Figures depict a vertical well, it should be noted by one skilled in the art that the apparatus for gravel packing an interval between mechanical packers is equally suited for use in deviated wells.

Gravel packing apparatus 100 includes vent screen 150, which comprises three main sections: filter section 152; blank pipe section 154; and removable vent section 156. During gravel packing operations, as shown in FIG. 2, gravel pack slurry 125 is delivered to the perforation tunnels 111 by workstring 103. Gravel pack slurry 125 is diverted around vent screen 150 by vent screen plug 158 and forced into the annular area 160 between vent screen 150 and casing 120. Check valve 170 is attached to the internal wall of vent screen 150 above filter section 152. Carrier fluid of gravel pack slurry 125 enters the vent section 156 of vent screen 150 and fills vent screen 150 internally from and above check valve 170. Check valve 170 prevents carrier fluid from entering filter section 152 and eliminates the potential for sand bridging as described above. Check valve 170 may be any type of check valve suitable for downhole use, but is preferably a ball type check.

Check valve 170 is attached to the internal wall of vent screen 150 by means of one or more shear pins 171, 172. Shear pins 171, 172 are designed such that when sandout pressure is achieved, shear pins 171, 172 will fail. By controlling the failure of shear pins 171, 172, the proper sand height 175 above formation 110 can be achieved. After failure of shear pins 171, 172, as shown in FIG. 3, check valve 170 falls to the bottom of vent screen 150, where it remains out of the direct path of reservoir fluids flowing from formation 110 into vent screen 150.

After sandout pressure has been achieved, vent section 156 may be removed from vent screen 150 by conventional means. Vent section 156 is attached to vent screen 150 by one or more shear pins 157, 158. Shear pins 157, 158 are sheared and vent section 156 is removed utilizing the appropriate tools and vent section 156 is removed to the surface through production string 103, leaving the full open diameter of vent screen 150 accessible to reservoir fluids. After vent section 156 has been removed, mechanical packer 104 is installed to minimize potential failure of the gravel pack. Mechanical packer 104 maybe installed as a stinger and sealed on the internal surface of vent screen 150, as shown in FIG. 3, or it may be installed as an overshot, which seals on the outside surface of vent screen 150 (not shown).

The exact design of filter section 152 and vent section 156 is not critical to the present invention as long as it is suitable designed for the characteristics of the formation fluids and solids and the gravel pack slurry. Filter section 152 and vent section 156 may comprise perforated pipe having wire wrap directly thereupon, or alternatively, may comprise a plurality of ribs around which wire is wrapped. Other suitable alternatives include sintered wire mesh or sintered metal.

FIGS. 4 and 5 illustrate another preferred embodiment of the present invention featuring a gravel packing apparatus 200 having a vented valve 280 that remains attached to the vent screen 250 after completion of the gravel pack. As described earlier, vent screen 250 comprises a filter section, 252, a blank pipe section 254, and a vent section 256. Vent section 256 comprises a lower screen portion 281 and a vented valve 280 mounted on top of the lower screen portion 281. Vented valve 280 comprises a check valve 282 that opens up into a vented, or slotted head 283.

Gravel packing operations employing gravel packing apparatus 200 is substantially similar to that for the removable vent gravel packing apparatus 100, shown in FIGS. 2 and 3. Gravel pack slurry is prevented from flowing down through slotted head 283 by check valve 282. Check valve 282 may be any suitable type of check valve, but is preferably a ball or plug type check. FIGS. 4 and 5 illustrate a ball type check having ball 284 and seat 286. Gravel pack slurry is further prevented from flowing through filter section 252 by check valve 270. Once the gravel pack is complete and shear pins 271, 272 fail causing check valve 270 to fall to the bottom of vent screen 250, mechanical packer 204 is installed which seals the annular region between packers 201,204 and formed by the external surface of vent screen 250 and the internal surface of casing 220. Once reservoir fluids are produced, ball 284 of check valve 282 lifts and allows reservoir fluids to flow through the seat 286 check valve 282, through the slots 285 of slotted head 283, and through production string 203 where the fluids will eventually reach the wellhead.

Although the present invention has been described in terms of specific embodiments, it is anticipated that alterations and modifications thereof will no doubt become apparent to those skilled in the art. It is therefore intended that the following claims be interpreted as covering all alterations and modifications that fall within the true spirit and scope of the invention. 

1. An apparatus for gravel packing an interval in a wellbore comprising: a tool body capable of being lowered into the wellbore; and a sand control vent screen positioned within the wellbore and having an upper and lower end, the upper end of the sand control vent screen comprising a removable vent section, coupled to the tool body, such that the tool body is capable of removing removable vent section.
 2. The apparatus of claim 1, wherein the sand control vent screen further comprises a blank pipe section having an upper and lower end, the upper end coupled to the removable vent sections, and a filter section having an upper and lower end, the upper coupled to the lower end of the blank pipe section.
 3. The apparatus of claim 2, wherein the upper end of the blank pipe section further comprises one or more shear pins, coupling the upper end of the blank pipe section to the removable vent section.
 4. The apparatus of claim 2, wherein the blank pipe section further comprises a check valve, disposed within the lower end of the blank pipe section such that fluid flow from within the blank pipe section to within the filter section is prohibited.
 5. The apparatus of claim 4, wherein the check valve further comprises one or more shear pins, coupling the check valve to the lower end of the blank pipe section.
 6. The apparatus of claim 5, wherein the shear pins are designed to fail when exposed to a predetermined shear force which results in the de-coupling of the check valve from the lower end of the blank pipe section.
 7. The apparatus of claim 6, wherein the check valve is a ball-type check valve.
 8. A method of gravel packing an interval in a cased wellbore comprising the steps of: running into the cased wellbore, a tool body coupled to a sand control vent screen, the sand control vent screen defining an annulus relative to the cased wellbore and having an upper and lower end, the upper end comprising a removable vent section; disposing sand control media within the annulus defined by the sand control vent screen and the cased wellbore; employing the tool body coupled to the sand control vent screen to remove the removable vent section: and installing a mechanical packer to isolate the annulus defined by the sand control vent screen and the cased wellbore.
 9. The method of claim 8, wherein the sand control vent screen further comprises: a blank pipe section having an upper and lower end, the upper end coupled to the removable vent sections; a filter section having an upper and lower end, the upper end coupled to the lower end of the blank pipe section; and a check valve, disposed within and coupled to the lower end of the blank pipe section such that fluid flow from within the blank pipe section to within the filter section is prohibited.
 10. The method of claim 9, further comprising the step of: causing the check valve to de-couple from the blank pipe section after depositing a predetermined quantity of sand control media within the annulus defined by the sand control vent screen and the cased wellbore.
 11. An apparatus for gravel packing an interval in a wellbore comprising: a tool body capable of being lowered into the wellbore; and a sand control vent screen positioned within the wellbore and having an upper and lower end, the upper end of the sand control vent screen comprising a vented valve assembly, the vented valve assembly comprising an upper housing having a plurality of openings defined therethrough a check valve disposed below and coupled to the upper housing, and a vent section disposed below and coupled to the check valve, such that when the check valve is open the vent section is in fluid communication with the upper housing.
 12. The apparatus of claim 11, wherein the sand control vent screen further comprises a blank pipe section having an upper and lower end, the upper end coupled to the vent section of the vented valve assembly, and a filter section having an upper and lower end, the upper end coupled to the lower end of the blank pipe section.
 13. The apparatus of claim 12, wherein the upper end of the blank pipe section is removably coupled to the vent section of the vented valve assembly.
 14. The apparatus of claim 13, wherein the upper end of the blank pipe section further comprises. one or more shear pins, coupling the upper end of the blank pipe section to the vent section of the vented valve assembly.
 15. The apparatus of claim 12, wherein the blank pipe section further comprises a second check valve disposed within the lower end of the blank pipe section ad such that fluid flow from within the blank pipe section to within the filter section is prohibited.
 16. The apparatus of claim 15, wherein the second check valve further comprises one or more shear pins coupling the check valve to the lower end of the blank pipe section.
 17. The apparatus of claim 16, wherein the shear pins are designed to fail when exposed to a predetermined shear force which results in the de-coupling of the check valve from the lower end of the blank pipe section.
 18. The apparatus of claim 17, wherein the check valve of the vented valve assembly and the second check valve are ball-type check valves.
 19. A method of gravel packing an interval containing production fluids in a cased wellbore comprising the steps of: running into the cased wellbore, a tool body coupled to a sand control vent screen the sand control vent screen defining an annulus relative to the cased wellbore and having an upper and lower end, the upper end comprising a vented valve assembly, the vented valve assembly comprising an upper housing having a plurality of openings defined therethrough, a check valve disposed below and coupled to the upper housing, and a vent section disposed below and coupled to the check valve, such that when the check valve is open the vent section is in fluid communication with the upper housing; disposing sand control media within the annulus defined by the sand control vent screen and the cased wellbore; installing a mechanical packer to isolate the annulus defined by the sand control vent screen and the cased wellbore.
 20. The method of claim 19, wherein the sand control vent screen further comprises: a blank pipe section having an upper and lower end, the upper end coupled to the vent section of the vented valve assembly; a filter section having an upper and lower end, the upper end coupled to the lower end of the blank pipe section; and a second check valve disposed within and coupled to the lower end of the blank pipe section such that fluid flow from within the blank pipe section to within the filter section is prohibited.
 21. The method of claim 20, further comprising the step of causing said second check valve to de-couple from the blank pipe section after depositing a predetermined quantity of sand control media within the annulus defined by the sand control vent screen and the cased wellbore. 